/**
 * A city's skyline is the outer contour of the silhouette formed by all the buildings in that city 
 * when viewed from a distance. Now suppose you are given the locations and height of all the buildings 
 * as shown on a cityscape photo (Figure A), write a program to output the skyline formed by these 
 * buildings collectively (Figure B).
 * 
 * 
 * The geometric information of each building is represented by a triplet of integers [Li, Ri, Hi], 
 * where Li and Ri are the x coordinates of the left and right edge of the ith building, respectively, 
 * and Hi is its height. It is guaranteed that 0 ≤ Li, Ri ≤ INT_MAX, 0 < Hi ≤ INT_MAX, and Ri - Li > 0. 
 * You may assume all buildings are perfect rectangles grounded on an absolutely flat surface at height 0.
 * For instance, the dimensions of all buildings in Figure A are recorded as: [ [2 9 10], [3 7 15], [5 12 12],
 * [15 20 10], [19 24 8] ] .
 * 
 * The output is a list of "key points" (red dots in Figure B) in the format of
 * [ [x1,y1], [x2, y2], [x3, y3], ... ] that uniquely defines a skyline. A key point is the left endpoint
 * of a horizontal line segment. Note that the last key point, where the rightmost building ends, is merely 
 * used to mark the termination of the skyline, and always has zero height. Also, the ground in between 
 * any two adjacent buildings should be considered part of the skyline contour.
 * 
 * For instance, the skyline in Figure B should be represented as:
 * [ [2 10], [3 15], [7 12], [12 0], [15 10], [20 8], [24, 0] ].
 */
/**
 * @author I321035
 *
 */
package problem218_The_Skyline_Problem;